Plant for track-based detection of the wheel profile of train wheels

ABSTRACT

An apparatus or system for a track-based detection of a wheel profile of passing train wheels, with the apparatus including an illumination unit with a light source and optical elements which transmit light towards a profile of the train wheels. An illumination area of the wheel profile is scanned with a scanning unit and a position of the wheel relative to the rail is scanned with a measuring unit. A data processing unit processes the data from the scanning unit relating to a condition of the wheel and a further unit is provided for transmitting the data concerning the condition of the wheels to at least a central processing unit.

FIELD OF THE INVENTION

The invention relates to an apparatus for track-based detection of awheel profile on a passing train and, more particularly, to an apparatuswherein when the train passes an optical unit of the apparatuscomprising an illumination device and a scanning unit for scanningreflective light, the profile of the train wheel is determined.

BACKGROUND OF THE INVENTION

Wear on the flanges and treads of railway wheel is a well-knownphenomenon, with the wear giving rise to increased operating costs andreduced safety if the presence of the defect is not quickly establishedso that the carriage in question can be taken out of service and berepaired at a time expedient for railway operations.

Usually, the presence of wear on railway wheels is ascertained by manualinspection of the treads and flanges of the wheels. This is a difficultprocedure to control, and there are also purely practical difficultiesin mechanically measuring and checking the wheel profile.

Today, the maintenance of the wheels is almost never effected on thebasis of a conditional supervision but on the basis of statisticalempirical data, with the result being that some wheels with defects arenot discovered and immediately repaired, while, on the other hand, manyfailure-free wheels are subjected to unnecessary inspection. However, itis known that the wear on treads and flanges can occur far more quicklythan expected, for example, because of insufficient rail lubrication orfollowing track repair work. Wheels with worn treads or flanges must,however, be repaired as quickly as possible after the defect has beenascertained, in that these wheel defects can result in greatly increasedwear and further possible damage. Moreover, worn wheels increase thepossibility of derailment, particularly when running in curves andthrough switch points.

In for example, PCT/DK87/00122, an apparatus for the scanning of thewheel profile on passing train wheels is proposed which is based on thewheel intersecting a skewed beam of light or pencil of rays during thesimultaneous measurement of the distance to the reflection point(s) onthe running surface. In practice, this apparatus functions as desired,but requires a measurement of the speed of the wheel in order to provideprecise information concerning the wheel profile.

European patent application no. 0,228,500 proposes an apparatus forcontact-less measurement of the wherein the wheel profile is illuminatedfrom underneath with a light edge. The scanning of the wheel profile iseffected tangentially to the wheel with one or more cameras, the signalsfrom which are processed electronically. This apparatus can onlyfunction with the use of a narrow auxiliary rail, so that almost all ofthe wheel profile can be illuminated from underneath, and, consequently,the apparatus can only be used during very slow running of the trainwheel and with unloaded carriages or in workshops where the wheels arelifted free of the rail element.

In German publication no. 3,526,923, an apparatus for the measuring ofwheel profiles is proposed wherein a skewed laser beam is intersected bya wheel as it passes, and, at the same time, a camera photographs theilluminated area. The resulting photographs of the wheel profile arecompared with pictures of correct wheels taken at the same angle. Asapparent such an apparatus can provide only a very rough picture of theextent of the wear on a wheel, and it can be assumed that the apparatuscan only be used to find very severe damages on the wheels.

SUMMARY OF THE INVENTION

The aim underlying the present invention resides in providing anapparatus for the track-based detection of the wheel profile on trainwheels which functions in a fully automatic manner while running atnormal operational speeds. The apparatus as capable of functioningwithout knowledge of the speed of the wheel, and is capable of detectingthe wheel profile on heavily loaded carriages during completely normaloperating conditions.

In accordance with advantageous features of the present invention, anapparatus for a track-based detection of a wheel profile of train wheelsis provided with the apparatus including an optical unit having anillumination device comprising a light source arranged for transmittingstructured light towards a profile surface of the wheel, with theillumination device being triggered by an actual position of the wheel.A scanning unit is provided which includes means for scanning reflectedlight from the profile surface of the wheel with a means also beingprovided for transferring the scanned signals to a data processing unit.A further unit measures or calculates the actual position of the wheelin a transverse direction, and means are provided for transferring datafrom the further unit to the data processing unit. The data processingunit at least processes, converts and corrects and, possibly, storesmeasured and calculated data and also supplies or is supplied withinformation concerning an optical axes of the illumination unit and thescanning unit. By virtue of the above-noted features of the presentinvention, the apparatus, as a unit, may be placed at the rail elementand can measure the wheel profile of all wheels on the train when itpasses the detection apparatus. Each time the illumination unit istriggered by a passing wheel, structured light is transmitted towardsthe wheel, e.g. from a flash light arrangement with suitable opticalelements, so that a desired pattern, e.g. a line or grid pattern, isprojected in on the profile surface of the wheel at an inclined anglefrom the apparatus, and the picture formed at the profile surface isscanned with a scanning unit, e.g. a CCD camera or the like, at acertain angle. By optical picture formation and consequent picturetreatment by suitable programs in the data processing unit, the profileof the wheel is calculated at the place of measurement. Alternatively,coefficients and other characteristic values of the wheel profile can becalculated. With flash-light, the wheel profile can be scanned in thismanner without having to know the train's speed of the train or wheel,but only the transverse or side position on the rail, a position whichcan be measured or calculated.

If the relevant stretch of track is used to carry carriages with wheelsof different sizes, the apparatus according to the invention means maybe provided for determining or measuring the size of the wheel with ameans for transferring data corresponding to the determined or measuredsize to the data processing unit. The information concerning the wheelsize can be used to trigger the illumination unit, or for the correctionof the measurement signals during the data processing.

In accordance with further features of the present invention, theapparatus may include at least one wheel detector placed on or at therail on which the wheel rolls. The wheel detector can be based, forexample, on magnetic induction, and can be used both for controlling thetriggering of the illumination device and for the ascertaining of thewheel size.

According to the present invention, a further light source may bearranged to illuminate one of the sides of the wheels, with a furtherscanning unit being arranged so as to scan at least a part of an edgearea of the illuminated side of the wheel. The additional scanning unitmay be coupled to a calculation circuit which is arranged to transferdata to the data processing unit the size of the wheel simultaneouslywith the scanning of the wheel profile, so that the profile measurementcan be corrected following the size of the wheel. This part of theapparatus will normally also be placed at the side of the rail element,but can possibly also be placed between the rails and measure on theinner side of the wheel. If this part of the apparatus is placed on afoundation independently of the rail element, one can also measure thedownwards deflections of the rail during the passing of the train inmanner described more fully below.

In accordance with the present invention, the light source may bearranged so as to shed a rectilinear pencil of rays on the profilesurface of the train wheel so that a line of light extends transverselyacross the surface of the wheel with the line or pencil of light beingscanned and the subsequent picture processing, and with knowledge of theangles between the light source, the scanning unit and the rail element,and with knowledge of the wheel size, data processing can hereafter becarried out so that the cross-sectional profile of the wheel orcharacteristic values of this profile can be obtained. By comparisonwith, for example, stored data for a perfect wheel, the apparatus canimmediately determine whether the wheel profile is worn too much, orwhether the profile still lies within acceptable tolerances.

Advantageously, the light source may be arranged to shed a number ofparallel rectilinear lines of light on the profile surface and beadapted to be focused at different distances from the light source. Afixed starting point can be used for triggering the illumination unitand measurement of the wheel profile on wheels of different sizes.Therefore, this embodiment is advantageous for use at stretches of thetrack which serve to carry carriages with wheels of different sizes.

According to the invention, the optical axes of the scanning unit may beskewed with respect to an axis of the wheel and may be directed at aninclined angle upwardly toward the illuminated area on the profilesurface, with a means being provided for correction of the downwarddeflection of the rail elements in the vertical direction as aconsequence of the weight of the train. Moreover, a position measuringunit may be arranged so as to be placed immediately at the side of therail element, with the measuring unit including a means for furthertransmission of measurement data. By virtue of these features, theapparatus can be placed at a suitable distance at the side of the railelement and be coupled to a wheel detector which indicates that a wheelis now in the correct position for measurement of the profile. If theapparatus is not arranged in such a manner that it follows the downwarddeflection of the rail under the weight of the train, correction can bemade for this by measuring the deflection. The resulting measured andcalculated data forms the basis for an automatic or manual qualitativeevaluation of how quickly the relevant wheel or the relevant carriageshall be taken out of service for repair. The entire measurement and theentire course of calculation usually takes place at measuring section.The data which are transmitted further from the apparatus generallyconsists solely of data which are representative of the condition of thewheel with regard to wear. Naturally, the plant can also be arranged sothat only data concerning wheels which are worn over and above a certainextent is transmitted further. This is of great practical value sincethere is frequently only access to a normal telephone line withconsequently poor transmission capacity.

In accordance with the present invention, a means may be provided fordetecting when a train enters the measuring area and also to detect whenthe last carriage leaves the area. Moreover, the wheel detector can beused to detect the size of the wheel, so that the plant is provided withinformation concerning the wheel size before or at the same time as themeasuring sequence is initiated.

In accordance with still further features of the present invention, awireless carriage identification system may be coupled to the dataprocessing unit and arranged in such a manner that measured orcalculated data for a wheel can be assigned to the carriageidentification, whereby the control of the amount of data isconsiderably simplified, and information concerning the condition of thewheel can be stored together with the carriage number, and possiblyinformation concerning which wheel on the carriage is involved.Furthermore, the carriage identification system can be used to providethe apparatus with data concerning the size of the wheels, e.g. byhaving the apparatus comprise a database containing associatedinformation concerning carriage numbers and wheel sizes.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described in closer detail with reference to apreferred embodiment and with reference to the drawing, wherein:

FIG. 1 shows the wheel profile of a perfect wheel,

FIG. 2 shows the wheel profile of a worn wheel,

FIG. 3 shows the detection apparatus according to the invention,

FIG. 4 is a sketch showing the measuring principle according to theinvention,

FIG. 5 is a sketch for explaining the measuring principle according tothe invention,

FIGS. 6, 7a, 7b and 8 show different sketches for explaining themeasuring principle according to the invention,

FIG. 9 shows a first embodiment for the measuring principle according tothe invention,

FIG. 10 shows a second embodiment for the measuring principle accordingto the invention, and

FIG. 11 shows a part of the plant for measuring the wheel size andpossible measurement of the downwards deflection of the rail.

DETAILED DESCRIPTION

Referring now to the drawings, wherein like reference numerals are usedthroughout the various views to designate like parts and, moreparticularly, to FIG. 1, according to this figure, a flanged wheel 1, inthe form of a wheel rolling on a rail 4, has a tread 2 and a flange 3with a cross-sectional profile corresponding to the for a perfect trainwheel, with the tread 2 and the flange 3 forming the profile surface ofthe wheel.

After having run for some time, the profile surface becomes wornresulting in for example a tread 2' and the flange profile 3', as shownin FIG. 2.

As shown in FIG. 3 the apparatus according to the invention includes alight source 9, for example, a flashing lamp in an illumination device6, is arranged to transmit light 12 towards the profile surface 2,3 onthe train wheel. In this case the light is a straight pencil of lightformed by a shutter 10 and a lens 11, e.g. a cylindrical lens. Since thelight is directed towards the surface at a certain angle, because theillumination device 6 has to be placed at the side of the rail elementso that the railway carriage can pass the apparatus, and because thelight is not directed on the wheel radially, an illuminated area 13 isobtained in the form of a curve, the shape of which depends both on thedirection of the optical axis of the illumination device 6 and on theshape of the profile surface, i.e. depending on the extent to which thewheel profile is worn. The illuminated area 13 is scanned with anoptical scanning unit 7 which, for example, can be a CCD camera with anoptical system 14 and a photocell matrix 15. The curve 13 is depicted onthe photocell matrix 15 at a certain angle, depending on the directionof the optical axis of the scanning unit 7.

The apparatus further includes a measuring unit 8 which measures theposition of the wheel with respect to the rail 4, e.g. by distancemeasurement with a transmitter and a receiver 17, e.g. using a laserbeam directed toward an inner side 5 of the wheel. The inner side 5 ofthe train wheel is normally used as reference for the profile surface.

All parts of the connected to a data processing unit 18 via suitableinterface equipment (not shown). To the data processing unit 18, orpossibly directly to the illumination device 6, there is fed a triggersignal 19 which triggers the light source in the illumination device 6,so that light in the form of a flash is directed on the profile surfacewhen the wheel is in correct position. The trigger signal is discussedin more detail later in connection with FIGS. 8-10.

The data processing unit 18 may also be supplied with information 23concerning the size of the wheel This information can be generated, forexample, from the signal from a wheel detector based on magneticinduction, or as information 25 from a commonly-known wireless carriageidentification system or in another known manner.

From the data processing unit 18, data can be transmitted, e.g. via atelephone line 20, to a central computer or to other surveillanceequipment or signal installation.

The measuring principle can, for example, be a form of triangulation onthe basis of the picture which the light of the profile surface, withknowledge of the axes of the optical units and their directions. In FIG.4 is seen the measuring principle with the use of optical pictureformation and subsequent picture processing. The illumination device 6directs light on the wheel profile, and depending on the angle of theillumination element and the angle of the scanning unit 7 to the surfacenorm a, a picture is obtained having a shape which depends on the heighth of the object.

A measure of the line displacement seen along the optical axis k of thescanning unit 7 can now be found in accordance with the relationships inFIG. 5 wherein;

k represents an optical axis of the scanning unit 7

l represents an optical axis of the rectilinear light from theillumination device 6

h represents the object height

θ_(S) represents the angle between the direction from "the runningdirection" a and the direction l to the illumination device

θ_(R) represents the angle between the direction from "the runningdirection" a and the direction k to the scanning unit

S_(S) represents the physical line displacement due to the object heighth

S_(R) represents line displacement due to the angle from θ_(R) to a Onecan now find the physical line displacement when taking intoconsideration a non-normal direction of vision in accordance with thefollowing equation represents a

    .increment.S.sub.S -.increment.S.sub.R =tanθ.sub.S ×h-tanθ.sub.R ×h

The line displacement observed by the scanning unit is determined byprojecting the physical line displacement in on the line of sight k ofthe scanning unit in accordance with the following equation: ##EQU1##

By virtue of the relationship expressed in equation (1), it is possibleto calculate the requirements for the resolution, sensitivity and therelevant angles of the overall system.

With commercially available scanning units 7, there are no problems inachieving a scanning precision of considerably less than 0.5 mm. If, forexample, a dot resolution of 1 mm is required and that train wheel has aprofile breadth of approximately 135 mm, the problem presented can besolved comfortably with a CCD camera of 500=582 picture dots.

As apparent from equation (1) the angles θ_(S) and θ_(R) are differentin order to obtain a line displacement at the profile height h. Forpractical reasons, for example because of the brake block around thewheels and also to enable measuring of small train wheels down todiameters of 350 mm, the structured rectilinear light must be projectedin on the wheel near to the rail element 4, for example, at about 100 mmthe rails.

If the line projection is parallel to the train (FIG. 6), the angleθ_(S) from the surface norm a to the illumination direction can becalculated. For small wheels with a radius of 175 mm, an angle θ_(S) of25° .4 is obtained, and an angle θ_(S) of 58° .2 is obtained for largewheel radii of 667 mm.

To achieve good utilization of the light from the illumination device,the angle θ_(R) (FIG. 5) must be as small as possible. With large wheeldiameters, it is difficult to obtain a small angle θ_(R), the reasonbeing that the rail shadows the field of vision of the scanning unit asapparent from FIGS. 7A and 7B. The shadowing 21 (FIG. 7B) can be avoidedby placing the scanning unit sufficiently far away from the center ofthe rail 4. When employing equation (1), the result obtained for the twowheel sizes mentioned above is:

    .increment..sub.S =0.475×h (radius 175 mm)

    .increment..sub.S =0.814×h (radius 667 mm)

which means that, without a considerable reduction in the CCD camera,surveillance can be carried out on wheels of all sizes.

The different wheel radii result in a line displacement on thephotosensitive dot matrix in the CCD camera. More particularly, as shownin FIG. 8. The pencil of light is directed at the height b of forexample 100 mm above the rail 4. This results in a change d of up to 193mm for the position of the wheel profile surface from a small diameterwheel to a large diameter wheel, i.e., for example, if one presupposes afixed position of the trigger device 22 for the triggering of theillumination device, independently of the wheel diameter size. In thedirection at right-angles to the optical axis of the CCD camera 7, thereoccurs a displacement c of up to 83 mm for the position of theilluminated area (the line) 13 on the profile surface, and therefore thedot matrix 15 of the CCD camera 7 must be of sufficient extent for theline 13 always to be depicted on the active matrix surface, regardlessof the degree of reduction which takes place in the lens system of thecamera.

A second solution possibility is shown in FIG. 9. One is able to ensurethat the distance the depiction point A on the wheel profile to theillumination device 6 and also to the scanning unit is alwaysindependent of the wheel size by changing the position of the point 22for that place/time at which the triggering of the illumination device 6is effected. The time at which a given wheel's wheel is at point A canbe ascertained, for example by means of a laser distance measuring unit,for example, of the Selcom type from Selcom AB, Sweden, and as discussedin the international patent application PCT/DK87/00122.

A third solution is shown in FIG. 10. A pencil of a plurality of rays 24which, for example, can be a pattern of lines focussed at differentdistances from the illumination unit 6', namely distances whichcorrespond to the different sizes of wheel diameters, are directed onthe profile surface. If the light rays 24 distributed, for example, over30 mm in the vertical direction, the possibility is provided of thecamera being able to observe an area e which lies within 0-41 mm, sothat picture formation takes place of all columns within the CCDcamera's matrix array, whereby surveillance can be carried out on allwheel sizes while using one fixed triggering point 22.

With all of the above-described embodiments of the invention, theflash-time for the illumination device 6,6' is such that the wheel doesnot move too much during the flash period, for example such that thewheel does not move more than 0.2 mm, which means that the flash musttake place within a period of around two microseconds. In practice, thisdoes not give rise to technical problems. Both measurements andcalculations have shown that no technical problems present themselves inobtaining sufficient light energy in the illuminated area for use to bemade of, for example, a CCD camera of the Fairchild CCD 4001 type. Witha suitably high light intensity, it is possible to use the apparatusaccording to the invention in broad daylight.

FIG. 11 provides an example of the manner by which during the passing ofthe train a direct measurement of the size of the wheel and the downwarddeflection of the rail under the weight of the train can be carried out.A light source 27, illuminates the outer side of the wheel (or possiblyan inner side) triggered by the data processing unit which controls theentire apparatus. The illuminated area, or at least a part hereof, whichincludes the edge of the wheel, is scanned by a camera 28, e.g. a CCDcamera. An electronic picture processing unit 29 then calculates thesize of the wheel, for example a diameter, of the wheel and transmitsthis information to the data processing unit 18. If the camera issupported in a fixed manner, for example, on an independent foundation,the apparatus can also calculate or scan the downward deflection of therail 4. Both of these measurements are carried out substantiallysimultaneously with the scanning of the wheel profile as explainedabove.

Furthermore, the apparatus can be arranged in such a manner that thecamera 28 can detect the light 12, 24 which is focussed on the profilesurface, so that the scanning point A on FIG. 9 is detected.

If the apparatus of FIG. 3 is extended with the arrangement shown inFIG. 11, the resulting apparatus can be placed directly at the railelement and undertake complete and precise wheel profile measurements ofpassing wheels.

We claim:
 1. An apparatus for a track-based detection of the wheelprofile of train wheels, the apparatus comprising:an optical unitincluding an illumination device having a light source arranged fortransmitting light towards a profile surface of the wheel, saidillumination device being triggered by an actual position; a scanningunit including means for scanning of light reflected from the profilesurface of the wheel and means for transferring scanned signals to adata processing unit; a further unit for at least one measuring orcalculating an actual position of the wheel on the rail with respect toa transverse direction of a rail upon which the wheel is running; andmeans for transferring data from said further unit to the dataprocessing unit, and wherein the data processing unit at leastprocesses, converts and corrects the measured or calculated data and oneof supplies or is supplied with information concerning an optical axesof the illumination and the scanning unit.
 2. An apparatus according toclaim 1, further comprising means for determining a size of the wheel,and means for transferring data from the determining means to the dataprocessing unit.
 3. An apparatus according to one of claim 1 or 2,further comprising at least one wheel detector disposed either on or atthe rail.
 4. An apparatus according to claim 2, wherein the means fordetermining comprises a further illumination unit including a furtherlight source for illuminating one side of the wheel, and a furtherscanning unit arranged so as to scan at least a part of an edge area ofan illuminated side of the wheel, and wherein the scanning unit iscoupled to a calculation circuit adapted to transfer data to the dataprocessing unit.
 5. An apparatus according to claim 1, wherein the lightsource is arranged so as to direct a rectilinear pattern of light rayson the profile surface so that a line of light extends transverselyacross the profile surface.
 6. An apparatus according to claim 1,wherein the light source is arranged so as to direct a plurality ofparallel rectilinear lines of light on the profile surface of the wheel,and wherein the lines of light are focussed at different distances fromthe light source.
 7. An apparatus according to one of claims 5 or 6,wherein an optical axis of the scanning unit is skewed with respect toan axis of the train wheel and is directed at an inclined angle upwardlytoward an illuminated area on the profile surface, and wherein means areprovided for correcting data relating to the surface profile of thewheel due to a downward deflection of the rail in a vertical directionresulting from a weight of the train.
 8. An apparatus according to claim1, wherein said further unit is arranged immediately adjacent a side ofthe rail, and wherein said further unit comprises means for enabling afurther transmission of data from said further unit to at least one of acentral processing unit, surveillance equipment or a signalinstallation.
 9. An apparatus according to one of claims 1 or 2, furthercomprising means for detecting when a train enters a profile detectionarea and for detecting when a last carriage of the train leaves theprofile detection area.
 10. An apparatus according to one of claim 1 or2, further comprising a wireless carriage identification system coupledto the data processing unit and being adapted to assign carriageidentification in dependence upon the measured or calculated data.